A conprehensive evaluation of diabetic glomerulonephropathy will be undertaken in a streptozotocin model of diabetes in the rat. Particularly, areas of investigation will include a study of the morphology of the model utilizing routine histologic techniques, immunopathology and electronmicroscopy. The dynamics of glomerular ultrafiltration in the diabetic model will be studied at 6, 12, 18 and 24 months utilizing established micropuncture techniques. Other studies are planned to elucidate the mechanism by which the renin-angiotensin-aldosterone system is suppressed in some patients with diabetes utilizing the animal model. In particular, morphologic study of the juxtaglomerular apparatus and serial assessment of plasma renin activity and aldosterone concentration will be done. In other studies, an attempt to produce Goldblatt hypertension will be done to determine if high intrarenal renin stores can be generated in the diabetic model. Other studies are designed to elucidate the mechanism by which hyperkalemia occurs in diabetes utilizing clearance techniques and in vitro aldosterone secretory rates in response to insulinopenia, insulin, potassium and glucose. The pathophysiology of radiographic contrast media induced acute renal failure will be studied in diabetic rats utilizing micropuncture methodology. Additionally, the protective effect of saline loading against acute renal failure will be evaluated in this model.